The present invention relates to an apparatus for slicing a cylindrical drum made of a thin metal sheet into a plurality of endless rings.
Belts for transmitting power in continuously variable transmissions, for example, use laminated rings of metal to bundle a plurality of elements that are arrayed in an annular endless pattern. Ring members of the laminated rings are produced by slicing, at certain axially spaced intervals, a cylindrical drum which is formed by welding opposite ends of a rectangular thin sheet of metal.
Heretofore, it has been known to slice a cylindrical drum at certain axially spaced intervals into ring members by clamping one end of the drum, pressing a rotating a grinding wheel or the like against an outer surface of the drum at the other end thereof, and moving the grinding wheel in a circumferential direction of the drum.
However, if the drum is sliced while it is being supported at one end thereof only, then since the drum is made of a thin metal sheet, the region of the drum pressed by the grinding wheel tends to be distorted, and the vibrations of the slicing apparatus are liable to be transmitted to the drum, vibrating the drum. As a result, the accuracy with which to slice the drum is lowered.
It is therefore an object of the present invention to provide a drum slicing apparatus which is capable of highly accurately and efficiently slicing a drum made of a thin metal sheet which is relatively highly flexible.
To achieve the above object, there is provided in accordance with the present invention an apparatus for slicing a cylindrical drum made of a thin metal sheet into a plurality of endless metal rings, comprising a support shaft rotatable about its own axis, a cylindrical drum holder supported on the support shaft for holding the drum by pressing engagement with an inner circumferential surface of the drum over an entire length thereof, and slicing means having slicing edges for slicing the drum into the metal rings by engaging and cutting into the drum at predetermined cutting positions thereon while the drum is being rotated by the support shaft through the drum holder.
The drum has recesses defined in opposite ends thereof, fully circumferential cut-off portions at the opposite ends including the recesses, and a ring forming region extending between the fully circumferential cut-off portions for forming the metal rings, the drum holder having engaging members for engaging in the recesses to prevent the fully circumferential cut-off portions from rotating when the drum holder holds the drum.
With the above arrangement, the drum is held by the drum holder, and rotated by the drum holder when the support shaft is rotated. The slicing edges of the slicing means are brought into abutment against the outer circumferential surface of the rotating drum at the predetermined cutting positions thereon, and cut into the drum in its circumferential direction, thus slicing the drum into the metal rings.
Since the drum is held with its inner circumferential surface pressed by the drum holder over the entire length of the drum, the drum, though it is made of a thin metal sheet, can be sliced by the slicing edges without being strained or vibrated. The drum can thus be sliced with high accuracy to produce highly accurate metal rings.
The drum is held by the drum holder with the engaging members engaging in the recesses. When the fully circumferential cut-off portions of the drum are cut off by the slicing edges, the fully circumferential cut-off portions are engaged by the engaging members against rotation. Therefore, even if the fully circumferential cut-off portions are of a relatively small width and are not sufficiently held in frictional engagement with the drum holder, the fully circumferential cut-off portions which have been cut off are reliably prevented from slipping on the drum holder and rotating in undulating motions, and hence from hitting and damaging the slicing edges.
The drum holder is removable from an end of the support shaft. Therefore, the drum can be mounted on and removed from the drum holder which has been removed from the support shaft. The drum can thus be mounted on and removed from the drum holder highly efficiently.
The support shaft comprises a main shaft rotatable about its own axis, a cylindrical collet disposed over the main shaft and radially spreadable by a plurality of axial slots defined in the cylindrical collet, and spreading means for radially spreading the cylindrical collet by widening the axial slots, the cylindrical drum holder having a plurality of axial slots defined therein which allow the cylindrical drum holder to spread radially, the arrangement being such that when the cylindrical drum holder is mounted on the cylindrical collet, the cylindrical drum holder is radially spreadable into pressing engagement with the inner circumferential surface of the drum in response to the cylindrical collet being spread by the spreading means.
The collet is radially spread by the spreading means, and the drum holder is radially spread as the collet is radially spread. That is, when the spreading means radially spreads the collet, the collet radially spreads the drum holder. When the drum holder is radially spread, the outer circumferential surface of the drum holder is pressed against the inner circumferential surface of the drum. The drum holder is thus pressed against the inner circumferential surface of the drum substantially uniformly over the entire length of the drum, for thereby holding the drum reliably highly accurately though the drum is relatively easily flexible. Since the drum holder can easily be removed from the collet when the collet is radially contracted, the drum holder can easily be removed from the support shaft.
The spreading means comprises a tapered surface disposed on the outer circumference of a proximal end of the main shaft at an end of the collet and progressively reduced in diameter toward a distal end of the main shaft, a tapered member movably mounted on the outer circumference of the distal end of the main shaft at an opposite end of the collet and axially movable on the main shaft, the tapered member being progressively reduced in diameter toward the proximal end of the main shaft, and a pressing member mounted on the distal end of the main shaft for engaging the tapered member, the arrangement being such that when the tapered member is pressed toward the tapered surface by the pressing member, the collet is radially spread by the tapered surface and the tapered member respective at the ends of the collet.
The tapered member is moved toward the tapered surface of the main shaft by the pressing member mounted on the distal end of the main shaft. As the tapered member is moved toward the tapered surface, the opposite ends of the collet slide against the tapered member and the tapered surface, radially spreading the collet uniformly over its entire length. When the collet is radially spread uniformly over its entire length, the drum holder mounted on the collet is also radially spread uniformly over its entire length, holding the drum highly accurately. When the pressing member is disabled to release the tapered member, the tapered member is moved away from the tapered surface of the main shaft, allowing the collet to be radially contracted uniformly over its entire length. The drum holder can therefore be removed from the collet smoothly and quickly.
The cylindrical drum is prepared by shaping a rectangular thin sheet of metal into a cylindrical form and butt-welding opposite ends of the rectangular thin sheet of metal, the recesses being used to position the opposite ends when the opposite ends are butt-welded. For forming the drum from the rectangular thin sheet of metal, the rectangular thin sheet of metal is curved into a cylindrical form, holding the opposite ends thereof against each other, and butt-welding the opposite ends. Since the opposite ends of the rectangular thin sheet of metal need to be welded highly accurately, the opposite ends that are held against each other are positioned using jigs engaging in the recesses. Since the opposite ends of the rectangular thin sheet of metal are thus positioned with the recesses for positioning these opposite ends, it is not necessary to form new recesses for positioning these opposite ends. Accordingly, a preparatory process for slicing the drum is simplified, and the efficiency of the slicing process is increased.
The slicing edges are spaced apart at intervals along an axial direction of the drum holder. The slicing edges cut into the drum at spaced intervals for simultaneously forming a plurality of metal rings of given width. Therefore, the metal rings can be produced from the drum highly efficiently.
The drum holder has a plurality of annular grooves defined in an outer circumferential surfaces in alignment with the respective predetermined cutting positions on the drum. When the slicing edges slice the drum, the slicing edges cutting into the drum and the drum holder are prevented from interfering with each other, and the drum can be sliced with increased accuracy.
The slicing means comprises a plurality of disk-shaped grinding wheels having abrasive grain slicing edges as the slicing edges on outer circumferential edges thereof for cutting into the predetermined cutting positions on the drum, further comprising dressing members disposed respectively in the annular grooves for dressing the abrasive grain slicing edges in sliding contact therewith when the abrasive grain slicing edges cut into the drum. When the abrasive grain slicing edges slice the drum supported on the drum holder, the abrasive grain slicing edges enter the annular grooves in the drum holder. Since the dressing members are disposed in the annular grooves, the abrasive grain slicing edges are held in sliding contact with the dressing members. Therefore, even when the abrasive grain slicing edges are loaded when they slice the drum, the abrasive grain slicing edges are immediately dressed by the dressing member. It is not necessary to remove the grinding wheels and dress the abrasive grain slicing edges when the abrasive grain slicing edges are loaded. The grinding wheels are thus efficiently dressed, and the abrasive grain slicing edges have their slicing capability maintained well without reducing the slicing efficiency.
The drum holder is radially contractible, further comprising ring removing means for radially contracting the drum holder which is removed from the support shaft while holding the metal rings sliced from the drum, thereby releasing the drum holder from pressing engagement with inner circumferential surfaces of the metal rings. The drum holder removed from the support shaft is radially contracted by the ring removing means and released from the inner circumferential surfaces of the metal rings, which are now released from being held by the drum holder. The metal rings which were held in intimate contact with the drum holder are prevented from suffering damage which would otherwise be caused by frictional contact between the circumferential wall of the drum holder and the inner circumferential surfaces of the metal rings when the metal rings are removed from the drum holder. The metal rings can thus be removed from the drum holder with ease. The metal rings can be removed in a highly accurate damage-free configuration.
Preferably, the drum holder has a pair of tapered surfaces disposed on respective upper and lower ends thereof and progressively reduced in diameter outwardly in an axial direction thereof, and the ring removing means comprises radially contracting means for holding the drum holder, with its axis directed vertically, removed from the support shaft, and radially contracting the drum holder, and a ring receiver disposed below the drum holder held by the radially contracting means, for receiving the metal rings released and dropped from the drum holder when the drum holder is radially contracted. The radially contracting means comprises a drum holder rest for placing the drum holder thereon in abutment against a lower end of the drum holder, a presser vertically movably disposed in confronting relation to the drum holder rest, for pressing an upper end of the drum holder downwardly, and lifting and lowering means for lifting and lowering the presser. The drum holder rest has a first slanted guide for slidingly engaging the tapered surface on the lower end of the drum holder to guide the drum holder in a direction to radially contract the drum holder, and the drum holder rest has a second slanted guide for slidingly engaging the tapered surface on the upper end of the drum holder to guide the drum holder in a direction to radially contract the drum holder.
With the drum holder and the ring removing means being thus constructed, the drum holder which is holding the metal rings sliced from the drum is placed, with its axis directed vertically, on the drum holder rest, and the presser presses the upper end of the drum holder. Then, the lifting and lowering means lowers the presser to cause the presser to press the drum holder axially. At this time, the tapered surface on the lower end of the drum holder is slidingly guided along the first slanted guide of the guide holder rest, and, at the same time, the tapered surface on the upper end of the drum holder is slidingly guided along the second slanted guide of the presser. The first and second slanted guides guide the drum holder in a direction to radially contract the drum through the tapered surfaces. The drum holder is thus radially contracted and released from the metal rings which have been supported on the outer circumferential surface of the drum holder, and the metal rings released from being supported by the drum holder drop onto the ring receiver by gravity.
When the drum holder is simply pressed and gripped between the drum holder rest and the presser, the metal rings can smoothly and quickly be removed from the drum holder without causing damage to the metal rings and the drum holder.
Since the drum can be sliced into highly accurate metal rings, the sliced metal rings may be used as ring members that are required to be highly accurate for bundling a plurality of elements arrayed in an endless pattern for use as a belt in a continuously variable transmission.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiments of the present invention by way of example.